1. Field of the Invention
This invention relates to the processing of rice to produce dehydrated rice, particularly for use in dehydrated foodstuffs such as soups and so-called "instant" foods or "no-cook" foods.
There is increasing commercial interest in dehydrated food preparations which can be rehydrated by the consumer in a few minutes by the addition of boiling water and which do not require any further cooking. Such food preparations can be sold in a container which also acts as a dish. The consumer adds boiling water to the food preparation and obtains a warm, cooked, palatable food which can be eaten after a few minutes. The necessary boiling water can be obtained from a kettle and there is no need for a cooker or a saucepan.
2. Description of the Prior Art
However there has not hitherto been any process available for the reliable production of rice which is suitable for use in "no-cook" food preparations and which is capable of rehydration to a palatable state in 2-3 minutes by the addition of boiling water therein, without additional cooking. Much work has been done in the field of quick-cooking rice (see "Technology of Quick-Cooking Rice" by B. P. Bhat, T. K. Chakrabarty and B. P. Bhatia in "Indian Food Packer", September-October 1972) but processes such as those of A. K. Ozai Durrani in U.S. Pat. Nos. 2,438,939 and 2,733,147 require the product to be further cooked by immersion in boiling water for 2-3 minutes (i.e. heating must be carried out to keep the water boiling) or by bringing the water back to the boil after the rice has been added to it. Disadvantages of the process of U.S. Pat. No. 2,438,939 are set out in Ozai Durrani's later U.S. Pat. No. 2,937,946. U.S. Pat. No. 2,733,147 and Ozai Durrani's British Pat. Nos. 657,691, 737,372 and 737,450 describe processes involving mechanical compression of the rice grain, which is difficult to carry out in large-scale production. British Pat. No. 437,446, also of Ozai Durrani, describes a process involving steaming and drying rice grains. The fact that so many proposals originated from the same inventor illustrates the problem in finding a satisfactory process for the production of a rice product which could be described as quick-cooking.
U.S. Pat. No. 2,715,579 of R. L. Roberts describes the preparation of a rice product which is said to be pre-cooked and whose preparation for the table involves absorption of boiling water without additional cooking. The Roberts' process involves soaking raw white rice in water until its moisture content is about 25 to 35%, heating the soaked rice to completely gelatinize the starch content of the grain without substantial increase in the moisture content thereof, drying the gelatinized grains to a moisture content from about 8 to 14%, and then expanding the dried grains in hot air at 200.degree.-260.degree. C. The present inventors have carried out tests on commercially available raw white rice and have found it to be an unsatisfactory starting material for the production of a "no-cook" rice by expansion or "puffing". When raw white rice of commerce is soaked, the present inventors have observed that a substantial proportion of grains have surface cracks which make the rice difficult to handle in subsequent processing. Also it has been observed that grains of raw white rice do not absorb water in a satisfactory manner in the soaking step.
In an earlier U.S. Pat. No. 2,616,808, R. L. Roberts described the use of parboiled rice in an expansion process to produce a ready-to-eat cereal product i.e. a product not intended to be rehydrated. However, Roberts did not suggest the use of parboiled rice for preparation of pre-cooked rice in the process of U.S. Pat. No. 2,715,579.